Fluid handling means



July 3, 1962 R. s. WADDINGTON ET AL 3,042,077

FLUID HANDLING MEANS 4 Sheets-Sheet 1 Filed Feb. 26, 1957 I n uen tor WAlJDl/V' TOIV 2? "ROGOR 6 RANGE A/va BRl/Cf D Attorney? July 3, 1962 R. s. WADDINGTON ET AL 3,042,077

FLUID HANDLING MEANS Filed Feb. 26, 195'? 4 Sheets-Sheet 2 lnvenlor ROGOR STRANGE WADDINGTO/V AND RZ/UE 01/) L A ftorney July 3, 1962 R. s. WADDXNGTON ET AL 3,042,077

FLUID HANDLING MEANS Filed Feb. 26, 1957 4 Sheets-Sheet 3 AND Inventors R0601? S T ANGE 4017/ GT BRUCE DUI/AL IV 04/ A tlorneys July 3, 1962 R. s. WADDINGTON ET AL 3,042,077

FLUID HANDLING MEANS 4 Sheets-Sheet 4 Filed Feb. 26, 1957 W w w w w M lnverl 0T5 R0601? STRANGE w/wmc fm Alva BRUCE DUI AL ate flaw 3,042,077 Patented July 3, 1962 FLUID HANDLING MEANS Rogor Strange Waddington, The Hayloft, 71 Dorking Road, Epsom, Surrey, England, and Bruce Duval,

39 Cheam Road, Ewell, Surrey, England Filed Feb. 26, 1957, Ser. No. 642,503 Claims priority, application Great Britain Feb. 27, 1956 7 Claims. (Cl. 137-604) The present invention relates to liquid-mixing apparatus of the type in which one liquid (the primaryliquid) is passed through a venturi passageway in such a manner that it draws another liquid (the secondary liquid) through a conduit communicating with the throat to provide a stream of mixed liquids.

For adjusting the concentration of the secondary-liquid in the mixture it is known to provide the secondaryliquid conduit with a control valve. While this control valve may be set to give complete interruption of the flow of the secondary-liquid through the secondaryliquid conduit, it is found in practice that when an attempt is made to obtain from the apparatus a stream of the primary-liquid by completely interrupting the flow of the secondary-liquid in the secondary-liquid conduit, the concentration of secondary-liquid in the primaryliquid is not immediately reduced to zero but after a sudden fall diminishes slowly. There is accordingly an appreciable period during which the stream of primaryliquid remains contaminated with the secondary-liquid. For many purposes this effect, which is a result of a pocket of secondary-liquid being left between the valve and the stream of primary-liquid on closure of the valve, if of no consequence, but where the secondary-liquid is one which substantially modifies the properties of the primary-liquid when present even in small concentrations therein, the efi'ect can be troublesome, the effect being particularly marked where the primary-liquid is water and the secondarydiquid is a surface active detergent. Many surface active detergents give rise to appreciable foaming when present in water in a concentration of only one part of active material per million parts by weight of water and consequently if the apparatus is intended for example to supply detergent solutions for cleaning purposes and plain water for drinking or cooking purposes it must be used with considerable care.

In accordance with the present invention there is provided apparatus for mixing liquids of the type suitable for connection to a water supply which comprises a venturi passageway and a secondary liquid conduit arranged as aforesaid and, for stopping the flow of secondary liquid when required, a valve having complementary surfaces on a seating part and a movable sealing means shaped to engage one another in fluid tight over-area engagement, the seating part being positioned substantially at the position where the conduit joins the throat.

As will be appreciated, the said sealing means, by sealing the bore of the secondary-liquid conduit at, or substantially at, its position of communication with the primary-liquid conduit, removes, or substantially removes, the ability for a pocket of the secondary-liquid to be left in contact with the stream of primary-liquid when delivery of the primary-liquid alone is required. It has been found in fact that within one second of using the apparatus for mixing surface-active detergents with water, water can be obtained therefrom which is so free from surface-active agent that it shows no tendency whatsoever to foam.

If desired the sealing means itself can be adapted to provide for adjustment of the flow of the secondaryliquid as well as for providing complete interruption of said flow and it is indeed within the scope of the present invention to provide the sealing means and the secondaryliquid conduit in such a mutual form that fine control of said flow can be achieved by movement of the sealing means in the secondary liquid conduit; for example the sealing means and the secondary-liquid conduit may 'be formed with co-operative conical surfaces. How ever, where fine control is required it is more economical to provide control valve means separate from the sealing element.

By the expression venturi passageway as used herein is meant a ilow pathway for the primarydiquid which is so shaped that the pressure of the secondarydiquid first falls and then rises again, and by the term throat" is meant the portion, or a portion, of the venturi passageway at which the pressure on the primary-liquid is reduced to a comparatively low level. Venturi passageways can take many different physical forms. In some, for example, the venturi passageway is of simple form being a conduit whose internal cross-section narrows to the throat and then widens again; in others, the form is more complex. For example, as with the venturi passageway of an ordinary laboratory filter pump, the throat may be a region contiguous with an annular aperture which provides communication between a chamber and an outlet from that chamber, the said annular aperture being bounded at its outer periphery by the outlet, and at its inner periphery by the end portion of a conduit which passes through the chamber.

A venturi of the last-mentioned type may be employed in accordance with the invention and it may be employed with the secondary-liquid conduit constituted either by the chamber or by the conduit which passes through the chamber. The former arrangement is, however, not preferred as it necessitates the provision of sealing means of annular form.

While an apparatus provided with a primary-liquid conduit in the form of a venturi passageway of any form may be employed in accordance with the said feature of the invention and gives successful results, it is found that venturi passageways of types hitherto known suffer from disadvantages which render them objectionable in practice. These disadvantages, and their solution by providing a special form of venturi passageway, are described in our co-pending application Serial No. 642,502, now Patent Number 2,980,033.

In most cases the source of the secondary-liquid will be a container into the bottom of which dips a tube leading to the secondary-liquid inlet passage. It might be expected that as the container is emptied and the head through which the secondary-liquid must be drawn correspondingly increased, the concentration of secondary-liquid in the mixed liquids would decrease significantly. This effect is not, however, important in practice since it is usually possible to arrange that the viscous drag on the flow of secondary-liquid product within the apparatus by the secondary-liquid inlet conduit and concentration control valve, if any, is substantial. Under these circumstances the effects of changes of head have their minimum effect. Where, using a can of detergent as the source of the secondary-liquid, the rate of drawing of the detergent would, in the total absence of viscous drag, have been twice the actually required maximum, no change of concentration was observed as the cam emptied. In a convenient construction, the movable sealing part is positioned in a valve chamber located adjacent to the throat section of the venturi passageway and communicating therewith via a port.

In cases where the port is so short in its axial length that the adjacent part of the valve chamber is itself positioned substantially at the throat, the sealing part may take the form of a sealing member adapted to cover the chamber end of the port and very satisfactory results have, for example, been obtained with an apparatus incorporating a valve chamber containing a piston for the fine-control of the flow of the secondary-liquid, in which apparatus the sealing means was provided in the form of a resilient pad mounted on the end of the piston and the length of the secondary liquid conduit was 0.010 inch. As will be appreciated, the provision of a port of such short length necessitates giving the material through which it is formed, a very small thickness; consequently if structural weakness is to be avoided the material must be an inherently durable one, preferably a metal. No difiiculty is encountered where the whole apparatus is formed of metal or an elastomer, but where the apparatus is formed of a hard synthetic resinous material, for example, polyvinyl chloride, polymethyl-methacrylate or polystyrene, it is advisable for the port, where short, to be formed through a metallic insert.

In order to illustrate the invention, there is given the following description of specific embodiments thereof, in which description reference is made to the accompanying drawings. In the drawings:

FIG. 1 shows in vertical cross-section a first device which incorporates a block valve assembly and a venturi of prefered type;

FIG. 2 is an elevation of the same device as viewed from the right of FIG. 1, the block valve assembly and parts 17, 27 and 28 being removed;

FIG. 3 is the cross-section taken along the line IIIIII of FIG. 2;

FIG. 4 is a vertical cross-section through a part of the device;

FIG. 5 a bottom view of the device as shown in FIG. 1, parts 53 and 54 being removed;

FIG. 6 is a planet the device shown in FIG. 1;

FIG. 7 illustrates a manner in which the device of FIGS. 1 to 6 may be put into use;

FIG. 8 shows a second device according to the invention which device incorporates a venturi of conventional type;

FIG. 9 is an exploded perspective view of a device which incorporates two block valve assemblies and a venturi of preferred type;

FIG. 10 is an enlarged perspective view of one of the valve blocks which form part of the device shown in FIG. 9;

FIG. 11 is a cross-section taken at level XIXI of FIG. 9; and

FIG. 12 is a longitudinal cross-section of that component part of the device shown in FIG. 9 which has the venturi passageway formed therein.

Referring to FIG. 1, the device shown therein comprises a body part 1 formed with a venturi passageway of the special shape described in our application Serial No. 642,502. This passageway having an inlet section 2, an elongated throat section 3 and an outlet section 4 connecting a primary-liquid inlet 5 with a mixture outlet 6. The diameter of the primary-liquid inlet 5 is W inch and the diameter of the mixture outlet 6 is inch. The inlet section 2 of the venturi passageway has a length of inch and an angle of convergence (half conical angle) of 12 /2". The elongated throat section 3 has a diameter of 7 inch and length of 1. inch, while the outlet section 4 has an angle of divergence (half conical angle) of 2 /2 and a length of 1 7 inches, giving a total length for'the body part and for the venturi passageway of 2 inches. As shown in our said application 642,502 the special shape at the venturi passageway gives it the properties of being able to function at a low head of primary liquid pressure without placing undue restriction on the primary liquid stream and of stabilising the concentration of the mixture produced against changes in the rate of primary liquid flow.

Water supply company regulations usually specify that the height of the lower end of a tap connected with the supply mains must be at least 3 inches above the top of the waste outlet from the sink or other fixed receptacle over which it is installed and that any anti-splash device or other extension connected with the tap must not exceed 3 inches in length. The result of these regulations is to avoid the submergence of the tap or any extension connected thereto below themaximum'water level, thereby avoiding any possibility of contaminated water being drawn back into the supply mains when the supply of water is interrupted. In consequence the overall length of the apparatus shown in the drawings is such as to render it acceptable virtually universally.

A secondary-liquid inlet passage 7 of diameter inch formed in the wall of the body part and entering the elongated throat section 3 at a distance of inch from the primary-liquid inlet 5 communicates with a valve chamber 8 also formed within the wall of the body part. As shown most clearly in FIG. 4, the outer end of the valve chamber is counter-sunk at 9 and contains a piston assembly (omitted for the sake of clarity from FIG. 1) which piston assembly consists of a stem 10 terminating in a piston 11 having a close fit within the valve chamber and, on the side of the piston opposite from the stem, a component 12 adapted to fill the conduit 7 substantially completely. The component 12 is, in the case shown, formed of soft rubber in order to provide a liquid-tight seal for the conduit 7. It may, however, be, and prefera'bly is, formed of hard steel or other metal ground to fit the passage closely. The stem part of the valve assembly passes through a rubber washer 13 which rests in the counter-sunk end of the valve chamber and whose central aperture has a close fit With the stem 10. The metal washer 14 placed over the rubber washer 13 serves to accept the reaction of the lower end of a helical spring 15 and the other end of which bears against a small knob 16 of nylon or other low-friction plastic material at the head-of the stem. The head 16 bears against the inner cam surface of the skirt of a cam ring 17 which is rotatably mounted upon the body part, the said skirt portion having a cylindrical inner surface which is formed eccentrically with the axis of rotation of the cam ring, thereby causing the piston 11 to be moved within the valve chamber when the cam ring is rotated. Index markings on the cam ring (not shown) enable the ring to be set for specific concentrations of secondary-liquid in the mixture. For limiting the rotation of the cam ring, and thus limiting outward movement of the piston, there is provided a rotatable set-ring 18 which carries a peg 19 adapted to engage a peg 20 which projects from the inner r surface of the cam ring. A set-screw 21, which is formed with a cruciform or other specially-shaped recess in its head so that it can only be moved by means of a complementary key is provided for locking the set ring 1 8 and consequently setting the stop 19 in a position corresponding with the desired maximum outward limit of travel of the piston assembly. Further limiting means for the rotation of the cam ring 17 are provided by a projection 22 formed on the body part, which projection is adapted to engage the ends 23 and 24 of a circular keyway formed in the under surface of the cam ring contiguous with the central aperture thereof. For locating the cam ring in its correct position upon the body part, the body part is formed with shoulders 25 and 26 adapted to co-operate with complementary formations surrounding the central aperture of the cam ring. A metal washer 27 retained in position by a split ring 28 which rests in the complementary groove 29 formed in the outer surface of the body part serves to hold the cam ring against withdrawal. Above the groove 29, the exterior of the body part is provided with a pair of grooves 30 and 31 which serveto assist in forming a strong connection when the device is connected by means of a short length of rubber tubing to the tap with which it is to be used. The external diameter' of the body part at this position is A inch.

For supplying the secondary-liquid to the valve chamher 8, there is provided an internal passageway 32 formed by making a long bore from the end of the body part to a small junction chamber 33 bored into the body part from a cylindrically walled flat-bottomed recess 34 formed in the outer surface thereof. The part of the long bore between the upper end of the body part and the valve chamber 8 is then filled throughout its length by means of a rod 35 cemented therein. In this way the passageway 32 is conveniently formed even though neither end is readily accessible for boring.

Secured to the side of the body part 1 with its end portion located within the recess 34 is a block valve assembly secured in position by screw 36 which enters a tapped hole 37 in the body part 1. A fibre gasket 38 placed in the bottom of the recess 34 ensures a fluidtight connection between the block valve assembly and the body part. The block valve assembly consists of a body part 39 formed with a large bore 40 which lies parallel with the axis of the venturi passageway in the body part 1 and extends from the under-surface of the part 39 to meet a short bore 41 formed coaxially therewith from the top of the part 39. Secured within the short bore 41 is a nipple 42. At its upper end the nipple 42 is provided with a seating surface 43 below which is formed a threaded section 44, this arrangement enabling a secondary-liquid supply tube to be secured by means of a suitable union nut. A horizontal bore 45 formed through the part 39 and passing through the bore 40 gives access during assembly to the screw 36. In the finally assembled device the outer end of the bore 45 is sealed by a plug 46 as shown. Located within the bore 40 is a tightly fitting plug'47 provided with a raised rim 48 at its lower end. A piston valve comprising a stem portion 49 of rounded triangular cross-section, a head portion 50 and a washer 51, has its stem passed in loose sliding relationship through a cylindrical bore 52 formed on the axis of the plug 47. The stem portion 49 of the piston assembly rests upon a rubber diaphragm 53 retained in position by a plug 54 provided with an upper circumferential ridge 55 which seals the lower end of the bore 4-0. The circumferential ridge 55 is perforated at 56 to provide communication between, on the one hand, the space between the underside of the diaphragm 53 and the upper surface of the plug 54, and on the other hand, a passageway 57 bored through the body part 39 at such an angle as to communicate with a junction chamber 58 formed in the recess in the body part 1. This junction chamber 58 communicates via a passageway 59 with the upper end of the body part 1. A further passageway 60 (FIG. 5) is formed through the part 39 to connect the junction chamber 33 with an aperture formed through the ridge 48 on the plug 47 and thence to the upper side of the diaphragm 53.

With the apparatus shown in FIGS. 1 to 6 connected with a tap or other supply of primary liquid by a short length of rubber tube having its end pushed over the grooves 30 and 31 and the nipple 42 connected with a supply of secondary-liquid, flow of the secondary-liquid to the valve chamber 8 is prevented until primary-liquid is passed through the venturi passageway and the pressure of the primary-liquid at the upper end of the apparatus is applied to the underside of the diaphragm 53 via passageway 59, junction chamber 58, passageway 57 and aperture 56. The efiect of this pressure is to deform the diaphragm and raise the piston 50 and washer 51 so that secondary liquid can flow through the clearance space between the stem 49 and the wall of the bore 52 to reach the valve chamber 8 via bore 60, junction chamber 33, and bore 32. Assuming that the cam ring 17 and consequently the piston assembly are in the relative positions shown in FIG. 4, the throttling eifect of the venturi passageway draws secondary-liquid into the stream of primary-liquid so that a mixture of primary and secondary liquids emerges from the mixture outlet 6, the actual strength of the mixture depending upon the precise position of the cam ring 17 and the corresponding position of the piston 11 relative to the orifice 61 with which the bore 32 communicates with the valve chamber 8. Outward movement of the piston 11 from the position shown in FIG. 4 causes the orifice to become relatively more uncovered and thus to increase the concentration of secondary-liquid in the mixture emerging from mixture outlet 6, while inward movement results in a more complete covering of the orifice 61 and thus reduces the said concentration. If while the primary-liquid is flowing the cam ring 17 is rotated to push the piston assembly inwardly by reaction of the head 16 thereof, to such an extent that part 12 fills or substantially fills the conduit 7, the supply of secondary-liquid is interrupted and moreover the complete filling or substantially complete filling of passage 7 by part 12 ensures that no pocket of secondaryliquid is left in contact with the stream of primary-liquid. Consequently, primary-liquid is almost immediately obtained from the mixture outlet 6 in uncontaminated condition.

When the flow of primary-liquid is interrupted its pressure ceases to be applied to the underside of the diaphragm 53. The washer 51 consequently falls into contact with the upper surface of the plug 47 and thus seals the secondary liquid supply from the valve chamber. If for any reason the outlet 6 is blocked and the primary liquid supply is operated in such a manner as to provide a vacuum elfect, secondary-liquid cannot be drawn into the primary-liquid supply.

The use of the device is illustrated diagrammatically in FIG. 7, which shows a tap A supplied by a pipe B leading, for example, from an overhead cistern or water supply mains and having the device attached thereto by means of a rubber connector C. A rubber or other tube D passes from the nipple and joins a copper tube E which dips to the bottom of detergent liquid in a can F placed under the sink G over which the tap A is installed. The lower end of the tube E is fitted with a housing I-I, adapted to pass through the mouth of the can and containing a filter for the detergent liquid and a non-return valve which ensures that the tube D and the secondary-liquid passageways in the device remain filled with detergent between mixing operations.

In FIG. 8 there is shown an alternative form of mixing device incorporating a venturi. This device consists of a chamber 71 adapted to be connected by a side tube 72 with a tap or other source of primary-liquid under pressure. Mounted within the top of the chamber 71 is a smaller chamber 73 adapted to be connected via a side tube 74 with a supply of secondary-liquid. At its lower end the secondary-liquid chamber is formed into a nozzle 75 which co-operates with an outlet pipe 76 to define a venturi throat 77. Located within the chamber 73 is a rod 78 formed at its lower end with an enlargement 79 to which is cemented a rubber sealing member 80 which is dimensioned to have a close fit with the inside nozzle 75. The upper end of the rod 78 passes through a threaded stutfing box 81 to terminate in a tap handle 82. Rotation of the tap handle 82 in one direction causes the sealing member 80 to be raised, thus allowing secondaryliquid to be drawn through the nozzle 75 and to mix with the primary-liquid in the outlet pipe 76. Rotating the tap handle 82 in the opposite direction causes the sealing member 80 to enter, and fill completely, the nozzle 75, thus enabling the flow of secondary liquid to be stopped completely and the primary-liquid to be obtained via outlet tube 76 substantially immediately in uncontaminated form.

In the embodiment shown in FIGURES 9 to 12 the body part consists of a moulding of vulcanised rubber. This body part consists of a tubular section 101 formed internally as shown in FIGURE 12 with a venturi pas sageway 102 dimensioned as described with reference to FIGURE 1. On its outer surface the tubular portion is formed with a pair of rectangular recesses bounded by radially projecting walls which co-operate therewith to ,of angular diameter 360 provide valve pockets 103 and 104 from the bottoms of which secondary-liquid inlet passages 105 and 106 communicate with the throat section of the venturi passageway 102. At the upper end of the device, the moulding is formed with a sleeve portion 107 by which it may be connected with a primary-liquid supply. Into the lower end of sleeve portion is press-fitted a metallic liner 108 formed with an apertured end wall 109 against the under surface of which is biased a valve plate 110 by a helical spring 111. The spring, sleeve and valve plate cooperate to form a valve which enables primary-liquid to flow through the apparatus in the direction of mixture outlet 112 but which serves to prevent mixture being sucked back in the opposite direction.

Within the valve pockets 103 and 104 are located metallic valve blocks "113 and 114 respectively. As will be seen most clearly from FIGURE 10, valve block 113 consists of a small block of metal bored to provide a valve chamber 115 and a secondary-liquid entry bore 116, which entry bore is internally threaded at its outer end to receive screw threaded nipple 117 for connection to a secondary-liquid supply tube 118. (FIGURE 11). At its inner end bore 116 is sealed by contact with the bottom of pocket 103.

Communication between the valve chamber 115 and the bore 116 is provided by forming a bore 119 from the end 120 of the valve block 113 and subsequently blocking the bore 119 at 121. The valve block 114 is similar to valve block 113 but has its secondary-liquid entry bore formed parallel with the bottom of pocket 104. A further secondary-liquid inlet supply tube 118a connects with the secondary-liquid entry bore of valve block 114 via a nipple 117a which passes through an aperture in the wall of pocket 104. (FIGURE 11).

For controlling the flow of secondary-liquid through passage 105, there is-provided a first piston assembly consisting of piston 123 having a close sliding fit within the valve chamber 115. At its inner face the piston is formed with a short cylindrical projection 124 adapted to seat over the secondary-liquid inlet passage where this joins the bottom of the pocket 103. At its outer face the piston is formed with a short piston rod 125, to the opposite end of which is secured a nylon button 126. For biasing the piston outwardly from the valve chamber there is provided a helical spring 127 which bears at one end upon the button 126 and at the other end upon a washer 128 which in turn bears against the face of the valve block via a rubber washer 129. For controlling the flow of secondary-liquid through passage 105 there is provided a second piston assembly which incorporates a piston 130 and is identical with the first piston assembly.

For adjusting the flow of secondary-liquid there is provided an outer moulding 131 formed of a vulcanised mixture of rubber and polystyrene. Whilst still hot this mixture is flexible and like a re-entrant moulding of ordinary rubber is easily withdrawable from the mould. When cold however it is, though still fairly flexible, much harder than an ordinary rubber moulding. At its lower end the outer moulding 131 is tapered to end in an annular bearing surface at 132 which seats upon a radial flange 133 formed round the outlet end of the body part. At its upper end the outer moulding 131 is formed with an inwardly directed flange 134 of angular diameter 270 which seats in a correspondingly dimensioned groove 135 formed round the lower end of the sleeve portion 107 of the body part. A small projection 136 formed in the groove 135 cooperates with the flange 134 in limiting the rotation of the outer moulding 131 to between angular limits separated by about 90. Of these limits, extreme anti-clockwise limit, as viewed from below, is the fully-off position for the secondaryliquid.

Slots formed through the wall of the outer moulding '131 co-operate to define flaps 137 and 13% in the wall thereof. Flap 137 is defined between a narrow upper slot 139, a wide lower slot 140 and a short end slot 141.

Flap 133 is similarly definedbetween upper, lower and end slots but the upper and lower slots are both narrow slots. The purpose of having slot wide is to enable the tubes 118 and 118a to pass therethrough. Outside the outer moulding 131 they'may be bound neatly together. Except when the outer moulding is rotated into or near the fully-off position, the inside faces of the flaps 137 and 130 bear as will be seen in FIG. 13 against the nylon buttons of the piston assemblies and their ends tend to be forced radially outwardly. In consequence the inside faces of the flaps provide cam surfaces for the buttons. The ends of the flaps bear against thin metal lugs 142 and 14-3 secured by screws 144 and 145 which are threaded into recess-ended bosses 146 and 147 moulded adjacent to the free ends of the flaps. The screw 144- has a head provided with a small cylindrical projection 148 and a hole 149 by which the screw can be turned easily only by using a complementary tool. A similar projection and hole are provided at the head of screw 145 for the same purpose.

The settings of the screws 1 14 and 145 define the inclination of the cam surfaces and hence the positions of the pistons as the outer moulding 131 is rotated from the fully-off position. The flow rates of secondary-liquid, which for a given flow rate of primary-liquid through the venturi passageway 102, depend upon the positions of the pistons relative to the end of the bore 119 and the corresponding bore in valve block 114 are independently adjustable by the screws 114 and 145.

When the outer moulding is rotated to the fully-off position the cylindrical projections of the pistonassern blies seat over the passages 105 and 106 at the bottoms of the pockets and thus ensure that the only residual quantities of secondary-liquids accessible to the primary-liquid flowing through the venturi passageway is the very small quantity retained in passages 105 and 106.

For use with a single secondary-liquid for example a detergent, tubes 118 and 118a can be connected with the same secondary-liquid supply, this arrangement being advantageous when the secondary-liquid must be drawn through a large head. Alternatively tube 118 only can be connected with the secondary-liquid supply and screw 145 can be adjusted so that no flow can occur through secondary liquid inlet passage 105. Tube 118a may indeed be removed. If required, tubes 118 and 118a can be connected with supplies to two different secondary liquids, for example a solution of a detergent and a solution of a sterilising agent such as sodium hypochlorite. The concentrations of the two secondary liquids in the mixture produced can then be controlled independently by screws 144 and 145. As solutions containing both detergent and a sterilising agent are often unstable, the embodiment illustrated in FIGURES 11 to 14 provides a very convenient device for forming such solutions in fresh form as required.

It will be appreciated that the specific embodiments of the mixing apparatus provided by the present invention which are described herein are given merely by way of illustration and that various departures may be made therefrom without departing from the scope of the invention claimed.

We claim:

1. Apparatus for mixing liquids which apparatus comprises a primary-liquid conduit formed with a venturi passageway having a convergent inlet section, an elongated throat section and a divergent outlet section, a valve chamber formed with a secondary-liquid inlet port for the supply of liquid thereinto, a secondary-liquid passageway leading from the valve chamber to the throat section of the venturi passageway, a movable valve member disposed in said chamber for covering said inlet port progressively, and a sealing part mounted on the valve member for sealing the secondary-liquid passageway substantially at its position of communciation with the throat section of the venturi passageway by fluid tight, over-area, engagement with the interior of the secondary liquid passageway.

2. Apparatus for mixing a secondary liquid with a primary liquid comprising a body part having a primary liquid inlet orifice at its upper end, an open outlet orifice at its lower end for the downward delivery of the liquid in a free stream and a venturi passageway for the passage of the primary liquid from within said inlet orifice to said outlet orifice, a secondary liquid conduit at the throat of said venturi passageway and in communication therewith and a valve having a sealing stem for engaging and sealing said secondary liquid conduit, said sealing stem and said secondary liquid conduit being formed with complementary surfaces shaped for mating in fluid tight, over-area engagement and positioned such that said engagement is obtained up to the throat of said venturi passageway.

3. Apparatus for mixing a secondary liquid with a primary liquid comprising a body part having a primary liquid inlet orifice at its upper end, an open outlet orifice at its lower end for the downward delivery of the liquid in a free stream and a venturi passageway for the passage of the primary liquid from within said inlet orifice to said outlet orifice, a valve chamber formed with a secondary liquid inlet port for the supply of secondary liquid thereinto, a thin wall portion common to said valve chamber and the throat of said venturi passageway and dividing said valve chamber from said throat, a port formed through said thin wall portion and a valve member movable within said valve chamber for engaging said thin wall port in fluid tight over-area engagement over a region contiguous with the periphery of said venturi passageway.

4. Apparatus for mixing a secondary liquid with a primary liquid comprising a body part having a primary liquid inlet orifice at its upper end, an open outlet orifice at its lower end for the downward delivery of liquid in a free stream and a venturi passageway for the passage of primary liquid from within said liquid inlet orifice to said outlet orifice, a valve chamber having a secondary liquid inlet port for the supply of secondary liquid thereinto, a thin wall portion common to said valve chamber and the throat of said venturi passageway and dividing said valve chamber from said throat, a port formed through said thin wall portion and a valve member operable by rnovement within said valve chamber to stop the flow of secondary liquid through said port sealing said port by fluid tight over-area engagement of a portion of said valve member with said thin wall portion over a region contiguous with the periphery of said port and also operable to regulate flow of secondary liquid through said valve chamber towards said port by action of a further portion thereof.

5. Apparatus for mixing liquids, which apparatus comprising a primary-liquid conduit formed with a venturi passageway, a valve chamber formed with a secondaryliquid inlet port for the supply of secondary-liquid thereinto, a thin wall portion common to the valve chamber and the primary-liquid conduit and dividing the valve chamber from the throat of the venturi passageway, a

secondary-liquid passageway formed through said thin wall portion and a valve member movable within said valve chamber to cover said secondary-liquid passageway in fluid tight over-area engagement therewith, a rotatable cam component formed of flexible material encircling said liquid conduit and mounted for rotation through a fixed angle for progressively moving said valve member over said inlet port and placing said valve member in said fluid tight engagement and said apparatus being provided with means for adjusting the inclination of said cam surface.

6. Apparatus for mixing liquids, which apparatus comprises a primary-liquid conduit formed with a venturi passageway, a valve chamber formed with a secondary-liquid inlet port for the supply of secondary-liquid thereinto, a thin wall portion common to the valve chamber and the primary-liquid conduit and dividing the valve chamber from the throat of the venturi passageway, a secondaryliquid passageway formed through said thin wall portion and a valve member movable within said valve chamber to cover said secondary-liquid passageway in fluid tight overarea engagement therewith, a rotatable member formed with a cam surface encircling said primary-liquid conduit for progressively moving said valve member over said inlet port and placing said valve member in said fluid tight engagement.

7. Apparatus for mixing liquids, which apparatus comprises a primary-liquid conduit formed with a venturi passageway, a valve chamber formed with a secondaryliquid inlet port for the supply of secondary-liquid thereinto, a thin wall portion common to the valve chamber and the primary-liquid conduit and dividing the valve chamber from the throat of the venturi passageway, a secondary-liquid passageway formed through said thin wall portion and a piston movable within said valve chamber to cover said secondary-liquid inlet port progressively and said secondary-liquid passageway in fluid tight, over-area engagement therewith.

References Cited in the file of this patent UNITED STATES PATENTS 911,000 Fitzgibbon Ian. 26, 1909 1,085,348 Ledoux Jan. 27, 1914 1,311,861 Earl July 29, 1919 1,321,856 Slater Nov. 18, 1919 1,748,488 McCabe Feb. 25, 1930 1,897,492 Ledoux Feb. 14, 1933 1,937,893 Hutton Dec. 5, 1933 2,168,363 Pos Aug. 8, 1939 2,300,642 Booth Nov. 3, 1942 2,353,759 Ray July 18, 1944 2,715,512 Miller Aug. 16, 1955 2,795,460 Bletcher et al. June 11, 1957 2,797,132 Alpert June 25, 1957 2,874,719 Van Tuyl Feb. 24, 1959 FOREIGN PATENTS 698,804 Germany Nov. 18, 1940 576,560 Great Britain Aug. 19, 1943 643,763 Great Britain Sept. 27, 1950 

